Method and apparatus for processing information, communications device, and communications system

ABSTRACT

This application discloses a method and an apparatus for processing information, a communications device, and a communications system. The communications device is configured to obtain a starting position of an output bit sequence in a coded block in a circular buffer, and determine the output bit sequence in the coded block based on a length of the output bit sequence and the starting position. A value of the starting position is one of {p 0 , p 1 , p 2 , . . . , p k     max     −1 }, where 0≤p k &lt;N CB , p k  is an integer, k is an integer, 0≤k&lt;k max , N CB  is a size of the coded block, and k max  is an integer greater than or equal to 4.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/529,438, filed on Aug. 1, 2019, which is a continuation ofInternational Application No. PCT/CN2018/074574, filed on Jan. 30, 2018,which claims priority to Chinese Patent Application No. 201710064621.X,filed on Feb. 4, 2017. All of the aforementioned patent applications arehereby incorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of the present invention relate to the communications field,and in particular, to a method and an apparatus for processinginformation, a communications device, and a communications system.

BACKGROUND

In a wireless communications system, a hybrid automatic repeat request(HARQ) technology is an important technology that can well improvereliability of a data link.

A low-density parity-check (LDPC) code is a type of linear block codehaving a sparse check matrix, and is characterized by a flexiblestructure and a low decoding complexity. Because the LDPC code uses apartially-parallel iteration decoding algorithm, the LDPC code has ahigher throughput than a conventional turbo code. The LDPC code may beused as a next-generation error-correcting code for communicationssystems and can be used to improve channel transmission reliability andpower utilization; and can be widely applied to space communications,fiber optic communications, personal communications systems, ADSLs,magnetic recording devices, and the like. Currently, in 5^(th)generation mobile communications, LDPC code scheme has been consideredas one of channel coding schemes.

To support various code lengths and code rates, a communications deviceperforms rate matching after channel coding to adjust a code rate of acoded block, and obtains a bit sequence that needs to be sent, so as tomatch a decoding code rate. During the rate matching, the communicationsdevice may further perform bit puncturing on LDPC coded blocks generatedafter the coding, to increase the code rate; or perform bit repetitionon the LDPC coded blocks generated after the coding, to decrease thecode rate.

In the rate matching process, a communications device at a transmit endselects a bit sequence that needs to be sent, performs processing suchas interleaving and mapping on the bit sequence, and sends the processedbit sequence to a communications device at a receive end. Thecommunications device at the receive end performs combining and decodingon soft values of the bit sequence and stored soft channel bits (softchannel bit) in decoding, to obtain a code block.

In the prior art, when the communications device at the transmit enduses an existing rate matching method, HARQ performance is relativelypoor.

SUMMARY

Embodiments of the present invention provide a method and an apparatusfor processing information, a communications device, and acommunications system, to improve HARQ performance.

According to a first aspect, a method for processing information in acommunications system is provided. The method includes:

obtaining a starting position k₀(i) of an output bit sequence in a codedblock; and

determining the output bit sequence in the coded block based on a lengthE(i) of the output bit sequence and the starting position k₀(i), wherethe coded block is stored in a circular buffer, and i is an integergreater than or equal to 0.

According to a second aspect, a method for processing information in acommunications system is provided. The method includes:

obtaining a starting position k₀(i) of a soft bit sequence having alength of E(i) stored in a soft buffer; and

combining and storing the soft bit sequence in the soft buffer startingfrom the starting position k₀(i).

In a possible implementation of the first aspect or the second aspect,for a retransmission, to be specific, for i>0, k₀(i) is determined basedon a starting position k₀(i−1) of a previous transmission output bitsequence and a length E(i−1) of the previous transmission output bitsequence. k₀(i)=(k₀(i−1)+F(i−1)) mod N_(CB). N_(CB) is a size of thecoded block, and F(i−1) is a bit quantity required for sequentiallyobtaining E(i−1) output bits from the coded block starting from k₀(i−1).

In this implementation, output bit sequences of two adjacenttransmissions are consecutive, and no repeated bit exists between thetwo output bit sequences, so that when such output bit sequences aresent to a communications device at a receive end, relatively gooddecoding performance can be achieved.

In a possible implementation based on the foregoing implementation, if abit at the end position in the coded block is transmitted,k₀(i)=(k₀(i−1)+F(i−1)+E_(offset)) mod N_(CB); otherwise,k₀(i)=(k₀(i−1)+F(i−1)) mod N_(CB).

In this implementation, after all bits are transmitted, a quantity ofrepeated bits is reduced, thereby reducing a decoding performance loss.

In another possible implementation of the first aspect or the secondaspect, a value of k₀(i) is p_(k) p_(k) is one of {p₀, p₁, p₂, . . . ,p_(k) _(max) ⁻¹}, 0≤p_(k)<N_(CB), p_(k) is an integer, k is an integer,0≤k<_(max), N_(CB) is a size of the coded block, and k_(max) is aninteger greater than or equal to 4.

For example, k_(max)=2″, and n is an integer greater than or equal to 2;or k_(max)=Nb, and Nb is a quantity of columns of a base matrix.

In another possible implementation based on the first aspect or thesecond aspect or the foregoing implementation, if k=0, p₀=l·z, where lis an integer, and 0≤l<Nb; or if 0<k<k_(max), P_(k)=(P_(k−1)+S) modN_(CB)·S is an integer. For example,

${S = \left\lfloor \frac{N_{CB}}{k_{\max}} \right\rfloor},{{{or}\mspace{14mu} S} = \left\lceil \frac{N_{CB}}{k_{\max}} \right\rceil},$or S=z, where z is a lifting size of the coded block. ┌ ┐ representsrounding up to an interger, and └ ┘ represents rounding down to aninterger.

By using

$S = {{\left\lfloor \frac{N_{CB}}{k_{\max}} \right\rfloor\mspace{14mu}{or}\mspace{14mu} S} = \left\lceil \frac{N_{CB}}{k_{\max}} \right\rceil}$as an example, p_(k)

$p_{k} = {{\left( {p_{k - 1} + \left\lfloor \frac{N_{CB}}{k_{\max}} \right\rfloor} \right){mod}\mspace{14mu} N_{CB}\mspace{14mu}{or}\mspace{14mu} p_{k}} = {\left( {p_{k - 1} + \left\lceil \frac{N_{CB}}{k_{\max}} \right\rceil} \right){mod}\mspace{14mu}{N_{CB}.}}}$For another example, p_(k) satisfies

${p_{k} = {\left( {p_{0} + \left\lfloor \frac{N_{CB} \cdot k}{k_{\max}} \right\rfloor} \right){mod}\mspace{14mu} N_{CB}}},{p_{k} = {\left( {p_{0} + \left\lceil \frac{N_{CB} \cdot k}{k_{\max}} \right\rceil} \right){mod}\ N_{CB}}},{p_{k} = {\left( {p_{0} + {k \cdot \left\lfloor \frac{N_{CB}}{k_{\max}} \right\rfloor}} \right){mod}\mspace{14mu} N_{CB}}}\;,{{{or}\mspace{14mu} p_{k}} = {\left( {p_{0} + {k \cdot \left\lceil \frac{N_{CB}}{k_{\max}} \right\rceil}} \right){mod}\mspace{14mu}{N_{CB}.}}}$

In an example in which S=z and z is the lifting size of the coded block,p_(k)=(k·z) mod N_(CB). In this implementation, a value of k_(max) maybe Nb, and Nb is the quantity of columns of the base matrix.

The foregoing method can adapt to various initial transmission coderates, so that an interval between redundancy version transmissions doesnot vary greatly or does not include a large quantity of repeated bits,thereby achieving relatively stable performance.

In another possible implementation of the first aspect or the secondaspect, a value of k₀(i) is p_(k), p_(k) is one of {p₀, p₁, p₂ . . . ,p_(k) _(max) ⁻¹} 0≤p_(k)<N_(CB), p_(k) is an integer, k is an integer,0≤k<k_(max), N_(CB) is a size of the coded block, and k_(max) is aninteger greater than or equal to 4.

For example, k_(max)=2″, and n is an integer greater than or equal to 2;or k_(max)=Nb, and Nb is a quantity of columns of a base matrix.

If p_(k)>(Nb−Mb+j)*z, p_(k) satisfies p_(k)−p_(k−1)≤p_(k+1)−p_(k), wherep_(m+1)=(Nb−Mb+j)*z, 0<m+1<k<k_(max−)1, j is a quantity of parity bitscorresponding to weight−2 columns in the coded block or j is a quantityof parity bits that correspond to weight-2 columns and that are notpunctured in the coded block, and z is a lifting size of the codedblock.

If p_(k)<(Nb−Mb+j)*z, p_(k) satisfies

$p_{k} = {\left( {p_{0} + \left\lfloor \frac{\left( {p_{m + 1} - p_{0}} \right) \cdot k}{m + 1} \right\rfloor} \right){mod}\mspace{14mu} p_{m + 1}\mspace{14mu}{or}}$${p_{k} = {\left( {p_{0} + \left\lceil \frac{\left( {p_{m + 1} - p_{0}} \right) \cdot k}{m + 1} \right\rceil} \right){mod}\ p_{m + 1}}},$where p_(m+1)=(Nb−Mb+j)*z, 0<k<m+1, j is the quantity of parity bitscorresponding to weight-2 columns in the coded block or j is thequantity of parity bits that correspond to weight-2 columns and that arenot punctured from the coded block, and z is the lifting size of thecoded block.

According to the method, starting positions are more densely distributedat positions closer to information bits, and starting positions are moresparsely distributed at positions closer to the last bit of the codedblock.

In the foregoing implementations, k_(max) may be an integer greater than4. For example, k_(max)=5; or k_(max)=2″, and k_(max) is 8 or above, forexample, 8 or 16, where n is an integer greater than 2. For anotherexample, k_(max)=Nb, and Nb is the quantity of columns of the basematrix of the coded block. An increase in k_(max) can reduce a distancebetween starting positions of redundancy versions. The redundancyversion determined based on the starting position can also improvedecoding performance of the communications device at the receive end.

In another possible implementation based on any one of the foregoingimplementations, for the retransmission, to be specific, for i>0, thestarting position k₀(i) is determined based on the starting positionk₀(i−1) of the previous transmission output bit sequence and the lengthE(i−1) of the previous transmission output bit sequence.

In a possible implementation, to reduce a quantity of repeatedredundancy bits, p_(k) is a minimum value satisfyingp_(k)≥((k₀(i−1)+F(i−1)) mod N_(CB)); or if ((k₀(i−1)+F(i−1)) mod N_(CB))is greater than a largest value in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹}p_(k) is a smallest value in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹}.

In another possible implementation, to meet a sequential decodingrequirement, P_(k) is a maximum value satisfying p_(k)≤((k₀(i−1)+F(i−1))mod N_(CB)); or if ((k₀(i−1)+F(i−1)) mod N_(CB)) is less than a smallestvalue in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} p_(k) is a largest valuein {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹}.

In another possible implementation, to compensate decoding performancelosses caused by repeating bits and by skipping redundancy bits, if p₀((k₀ (i−1)+F(i−1)) mod N_(CB))≤p_(k) _(max) ⁻¹, p_(k) is a value in {p₀,p₁, p₂ . . . , p_(k) _(max) ⁻¹} that has a smallest difference with ((k₀(i−1)+F(i−1)) mod N_(CB)); or if ((k₀ (i−1)+F(i−1)) mod N_(CB)) is lessthan a smallest value in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} or ((k₀(i−1)+F(i−1)) mod N_(CB)) is greater than a largest value in {p₀, p₁, p₂. . . , p_(k) _(max) ⁻¹} p_(k) is one of the smallest value in {p₀, p₁,p₂ . . . , p_(k) _(max) ⁻¹} and the largest valu p_(k) _(max) ⁻¹ in {p₀,p₁, p₂ . . . , p_(k) _(max) ⁻¹} that has a smaller difference with ((k₀(i−1)+F(i−1)) mod N_(CB)).

In another possible implementation, to compensate decoding performancelosses caused by repeating bits and by skipping redundancy bits, thestarting position k₀(i) is determined based on the starting positionk₀(i−1) of the previous transmission output bit sequence, the lengthE(i−1) of the previous transmission output bit sequence, and a quantityi of transmissions.

In the foregoing implementations, F(i−1) is a bit quantity required forsequentially obtaining E(i−1) output bits from the coded block startingfrom k₀(i−1).

In another possible implementation based on any one of the foregoingimplementations, the starting position k₀(i) is determined based on aredundancy version starting position number rv_(idx)(i).

For example, for an adaptive retransmission, the redundancy versionnumber rv_(idx)(i) may be obtained through signaling.

For another example, for an adaptive retransmission or a non-adaptiveretransmission, the redundancy version starting position number rv_(idx)may be obtained based on a sequence of redundancy version startingposition numbers and a quantity i of transmissions.

The sequence of the redundancy version starting position numbers isretrieved from a memory, or the numbering sequence of the redundancyversion starting positions is determined based on an initialtransmission code rate, or the sequence of the redundancy versionstarting position numbers is determined based on the length of theoutput bit sequence and the lifting size z.

According to a third aspect, an apparatus for processing information ina communications system is provided. The apparatus includes:

an obtaining unit, configured to obtain a starting position k₀(i) of anoutput bit sequence in a coded block; and a processing unit, configuredto determine the output bit sequence in the coded block based on alength E(i) of the output bit sequence and the starting position k₀(i),where the coded block is stored in a circular buffer, and i is aninteger greater than or equal to 0.

The apparatus may be configured to perform the method according to thefirst aspect or any possible implementation of the first aspect. Fordetails, refer to the description of the foregoing aspect.

In a possible design, the apparatus for processing information accordingto this application may include a module correspondingly configured toperform the first aspect or any possible implementation of the firstaspect in the foregoing method design. The module may be software and/orhardware.

According to a fourth aspect, an apparatus for processing information ina communications system is provided. The apparatus includes:

an obtaining unit, configured to obtain a starting position k₀(i) of asoft bit sequence having a length of E(i) stored in a soft buffer; and aprocessing unit, configured to combine and store the obtained soft bitsequence in the soft buffer starting from the starting position k₀(i).

The apparatus may be configured to perform the method according to thesecond aspect or any possible implementation of the second aspect. Fordetails, refer to the description of the foregoing aspect.

In a possible design, the apparatus for processing information accordingto this application may include a module correspondingly configured toperform the second aspect or any possible implementation of the secondaspect in the foregoing method design. The module may be software and/orhardware.

According to a fifth aspect, a communications device is provided. Thecommunications device includes an encoder, a rate matcher, and atransceiver.

The encoder is configured to encode information data.

The rate matcher includes the apparatus for processing informationaccording to the third aspect, and is configured to determine the outputbit sequence in the foregoing embodiments.

The transceiver is configured to send a signal corresponding to theoutput bit sequence from the rate matcher.

According to a sixth aspect, a communications device is provided. Thecommunications device includes a decoder, a rate de-matcher, and atransceiver.

The transceiver is configured to receive a signal corresponding to thesoft bit sequence of the output bit sequence in the foregoing aspect.

The decoder is configured to decode soft channel bits in a soft buffer.

The rate de-matcher includes the apparatus for processing informationaccording to the fourth aspect, and is configured to combine and storethe soft channel bits of the output bit sequence in the foregoing aspectin the soft buffer.

According to a seventh aspect, an embodiment of the present inventionprovides a communications system. The system includes the communicationsdevice according to the fifth aspect and the communications deviceaccording to the sixth aspect.

According to another aspect, an embodiment of the present inventionprovides a computer storage medium including a program designed toexecute the foregoing aspects.

According to still another aspect of this application, a computerprogram product including instructions is provided. When the computerprogram product is run on a computer, cause the computer to perform themethods according to the foregoing aspects.

According to the method and apparatus for processing information, thecommunications device, and the communications system in the embodimentsof the present invention, the output bit sequence for the initialtransmission or the retransmission is properly determined, so thatdecoding performance of the communications device at the receive endafter receiving the soft bit sequence of the output bit sequence isimproved, a decoding success rate is improved, and a quantity ofretransmissions is further reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a base matrix of an LDPC code andpermutation matrices;

FIG. 2 is a schematic structural diagram of a parity check matrix of anLDPC code;

FIG. 3 is a structural diagram of a communications system according toan embodiment of the present invention;

FIG. 4 is a flowchart of a method for processing information accordingto another embodiment of the present invention;

FIG. 5-1 is a schematic diagram of a coded block according to anotherembodiment of the present invention;

FIG. 5-2 is a schematic diagram of a coded block according to anotherembodiment of the present invention;

FIG. 5-3 is a schematic diagram of a coded block according to anotherembodiment of the present invention;

FIG. 6 is a flowchart of a method for processing information accordingto another embodiment of the present invention;

FIG. 7 is a structural diagram of an apparatus for processinginformation according to another embodiment of the present invention;

FIG. 8 is a structural diagram of an apparatus for processinginformation according to another embodiment of the present invention;

FIG. 9 is a structural diagram of a communications device according toanother embodiment of the present invention; and

FIG. 10 is a structural diagram of a communications device according toanother embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following describes technical solutions in embodiments of thepresent invention with reference to the accompanying drawings in theembodiments of the present invention.

FIG. 1 is a schematic diagram of a base matrix of an LDPC code in acommunications system and permutation matrices. The base matrix of theLDPC code includes m_(H)*n_(H) elements, wherein m_(H) is a row count ofthe base matrix, n_(H) is a column count of the base matrix. If the basematrix is lifted by using z as a lifting size, an (m_(H)*z)*(n_(H)*z)parity check matrix H may be obtained. To be specific, the parity checkmatrix H includes m_(H)*n_(H) blocks. Each block is obtained byperforming cyclic shift on an identity matrix of size z*z. The liftingsize z is usually determined based on a code block size supported by thesystem and an information data amount. FIG. 1 shows a base matrix,having a QC structure, of an LDPC code, where m_(H)=13, and n_(H)=38. Acode rate of the base matrix is (n_(H)−m_(H))/n_(H)=0.6579. If thelifting size z=4, each element whose value is −1 in the matrix is liftedto an all-zero matrix of size 4*4, and other elements are lifted topermutation matrices of size 4*4. The permutation matrix may be obtainedby performing cyclic shift on an identity matrix I for a correspondingquantity of times, and the quantity of shifts is equal to a value of acorresponding matrix element. As shown in FIG. 1 , a correspondingpermutation matrix obtained after an element whose value is 0 in thebase matrix is lifted is an identity matrix I of size 4*4, acorresponding permutation matrix obtained after an element whose valueis 1 is lifted is a matrix obtained by shifting an identity matrix once,and so on. Details are not described herein again.

After being lifted, the base matrix may be used as a parity check matrixused for encoding or decoding of the LDPC code. An LDPC code having acode length nil and an information sequence length k_(c) is marked as an(n_(H), k_(c)) LDPC code and may be uniquely determined by the paritycheck matrix H. The parity check matrix H is a sparse matrix, where eachrow of the check matrix H represents one parity check equationconstraint and corresponds to j coded bits, each column represents onecoded bit constrained by m_(H) parity check equations, and any twoparity check equations include at most one same coded bit. An example ofa parity check matrix H of the LDPC code and a corresponding paritycheck equation is given in the following formula (1):

$\begin{matrix}{H = \left. \begin{matrix}{{v_{0}\mspace{20mu} v_{1}\mspace{11mu} v_{2}\mspace{14mu} v_{3}\mspace{14mu} v_{4}\mspace{14mu} v_{5}\mspace{14mu} v_{6}\mspace{14mu} v_{7}\mspace{14mu} v_{8}\mspace{14mu} v_{9}}\mspace{20mu}} \\{\begin{Bmatrix}1 & 1 & 1 & 1 & 0 & 0 & 0 & 0 & 0 & 0 \\1 & 0 & 0 & 0 & 1 & 1 & 1 & 0 & 0 & 0 \\0 & 1 & 0 & 0 & 1 & 0 & 0 & 1 & 1 & 0 \\0 & 0 & 1 & 0 & 0 & 1 & 1 & 0 & 0 & 1 \\0 & 0 & 0 & 1 & 0 & 0 & 0 & 1 & 1 & 1\end{Bmatrix}\begin{matrix}c_{0} \\c_{1} \\c_{2} \\c_{3} \\c_{4}\end{matrix}}\end{matrix}\rightarrow\left\{ \begin{matrix}{{v_{0} + v_{1} + v_{2} + v_{3}} = 0} \\{{v_{0} + v_{4} + v_{5} + v_{6}} = 0} \\{{v_{1} + v_{4} + v_{7} + v_{8}} = 0} \\{{v_{2} + v_{5} + v_{6} + v_{9}} = 0} \\{{v_{3} + v_{7} + v_{8} + v_{9}} = 0}\end{matrix} \right. \right.} & (1)\end{matrix}$

FIG. 2 shows an example of a parity check matrix H of the LDPC code. Asshown in FIG. 2 , the parity check matrix includes a kernel matrix andthree extended matrix parts. Information data may be encoded and decodedby using four parity check matrices: a kernel matrix; a parity checkmatrix 1 including the kernel matrix and an extended matrix part 1; aparity check matrix 2 including the kernel matrix, the extended matrixpart 1, and an extended matrix part 2; a complete matrix including thekernel matrix, the extended matrix part 1, the extended matrix part 2,and an extended matrix part 3. The parity check matrices each has aRaptor-like structure. The part corresponding to parity bits has dualstructures, namely, a bidiagonal structure and a weight-1 columnstructure. The kernel matrix usually includes a bidiagonal structurepart. If a quantity of information bits before coding is k, and a codelength of an LDPC coded block generated based on the parity check matrixis n, a code rate is k_(c)/n_(H). LDPC coded blocks having differentcode rates may be obtained by using different parity check matrices forencoding. It may be learned that in the coded blocks, an LDPC codewordgenerated based on the complete matrix has a largest code length and hasa lowest code rate R_(min); an LDPC codeword generated based on thekernel matrix has a smallest code length and has a highest code rateR_(max); an LDPC codeword generated based on the parity check matrix 1has a code rate R₁; and an LDPC codeword generated based on the paritycheck matrix 2 has a code rate R₂, and R_(min)<R₂<R₁<R_(max). It shouldbe noted that in the foregoing example, the complete matrix, the kernelmatrix, the parity check matrix 1, or the parity check matrix 2 may allbe used as a base matrix of the LDPC code, which can be lifted accordingto the lifting size to obtain a matrix for encoding or decoding.

In the communications system, transmission of information data betweencommunications devices (for example, base stations or terminals) issusceptible to interference and errors, because a radio propagationenvironment is complex and variable. To reliably send information data,a communications device at a transmit end performs processing such asCRC attachment, channel coding, rate matching, and interleaving on theinformation data, maps interleaved coded bits into modulation symbols,and sends the modulation symbols to a communications device at a receiveend. After receiving the modulation symbols, the receiving devicecorrespondingly performs de-interleaving, rate de-matching, decoding,and CRC to recover the information data. These processes can reducetransmission errors and improve reliability of data transmission.

A communications system 300 shown in FIG. 3 may be widely applied tovarious types of communication such as voice communication and datacommunication. The communications system may include a plurality ofwireless communications devices. For clarity, FIG. 3 shows only acommunications device 30 and a communications device 31. Controlinformation or data information is sent and received as an informationsequence between the communications device 30 and the communicationsdevice 31. The communications device 30 serves as a communicationsdevice at a transmit end, to send the information sequence in transportblocks (transmission block, TB), and attaches CRC bits to each transportblock. If a size of a transport block with CRC attachment exceeds alargest code block length, the transport block needs to be segmentedinto several code blocks (code block, CB). Code block CRC bits may alsobe attached to each code block, or code block group CRC bits may beattached to each group of code blocks, and filler bits may be furtherinserted into each code block. The communications device 30 performschannel coding on each code block, for example, performs LDPC coding toobtain a corresponding coded block. Each coded block includesinformation bits and parity bits. If the information bits include afiller bit, the filler bit is usually expressed as “null” (Null).

A coded block or a coded block on which bit rearrangement has beenperformed is stored in a circular buffer of the communications device30, and the communications device 30 sequentially obtains a plurality ofoutput bits from the coded block stored in the circular buffer, toobtain an output bit sequence. An output bit is a bit other than afiller bit in the coded block, and therefore the output bit sequencedoes not include any filler bit. The output bit sequence is sent afterbeing interleaved and mapped into modulation symbols. When performing aretransmission, the communications device 30 selects another output bitsequence from the coded block in the circular buffer and sends theanother output bit sequence. If obtaining the output bits sequentiallyreaches a last bit of the circular buffer, selection of an output bitcontinues starting from a start bit of the circular buffer.

After demodulating and de-interleaving the received modulation symbols,the communications device 31 stores soft values of the received outputbit sequence in a corresponding position in a soft buffer (soft buffer).If retransmissions occur, the communications device 31 combines softvalues of output bit sequences in all retransmissions and stores thecombined soft values in the soft buffer. Combining herein means that ifpositions of output bits received at two transmissions are the same,soft values of the output bits received at the two transmissions arecombined. Positions in the soft buffer of the communications device 31are in a one-to-one correspondence with positions in the coded block inthe circular buffer of the communications device 30. To be specific, ifthe position of the output bit in the coded block in the circular bufferof the communications device 30 is a p^(th) bit, the position of thesoft value of the output bit in the soft buffer of the communicationsdevice 31 is also a p^(th) bit.

The communications device 31 decodes all soft values in the soft bufferto obtain a code block of an information sequence. The communicationsdevice 31 may obtain a transport block size. Therefore, a quantity ofcode blocks into which one transport block is segmented and a length ofeach code block may be determined. If the code block includes a CRC bitsegment, the communications device 31 may further use the CRC bitsegment to check the code block. The communications device 31concatenates all the code blocks into one transport block, and furtherperforms checking and concatenation on transport blocks to finallyobtain the information sequence. It may be learned that thecommunications device 31 performs a reverse process of a method forprocessing information performed by the communications device 30.

It should be noted that in the embodiments of the present invention, thecommunications device 30 may be a network device such as a base stationin the communications system, and correspondingly the communicationsdevice 31 may be a terminal. Alternatively, the communications device 30may be a terminal in the communications system, and correspondingly thecommunications device 31 may be a network device such as a base stationin the communications system.

For ease of understanding, some terms used in this application aredescribed below.

In this application, terms “network” and “system” are often alternatelyused, but a person skilled in the art may understand their meanings. Theterminal is a device having a communication function, and may include ahandheld device having a wireless communication function, an in-vehicledevice, a wearable device, a computing device, or another processingdevice connected to a wireless modem. The terminal may have differentnames in different networks, for example, user equipment, a mobilestation, a subscriber unit, a station, a cellular phone, a personaldigital assistant, a wireless modem, a wireless communications device, ahandheld device, a laptop computer, a cordless telephone set, or awireless local loop station. For ease of description, the terminaldevice is briefly referred to as a terminal in this application. Thebase station (base station, BS) may also be referred to as a basestation device, and is a device deployed in a radio access network toprovide a wireless communication function. In different wireless accesssystems, the base station may have different names. For example, a basestation in a universal mobile telecommunications system (UniversalMobile Telecommunications System, UMTS) network is referred to as aNodeB (NodeB), a base station in an LTE network is referred to as anevolved NodeB (evolved NodeB, eNB or eNodeB), a base station in a newradio (new radio, NR) network is referred to as a transmission receptionpoint (transmission reception point, TRP) or a next generation NodeB(generation NodeB, gNB), or base stations in various other evolvednetworks may also have other names. The present invention is not limitedthereto.

FIG. 4 is a schematic flowchart of a method for processing informationaccording to an embodiment of the present invention. The method may beapplied to a communications system. The communications system includes acommunications device 30 and a communications device 31. The method maybe implemented by the communications device 30 and includes thefollowing steps.

401: Obtain a starting position k₀(i) of an output bit sequence in acoded block.

In the communications device 30, the coded block is stored in a circularbuffer. A size of the coded block may be represented by N_(CB). Thecoded block may also include one or more filler bits. When the codedblock is initially transmission or retransmission, the communicationsdevice 30 determines, in the coded block in the circular buffer, theoutput bit sequence used for the initial transmission or theretransmission. The output bit sequence does not include any filler bit.For ease of description, an i^(th) transmission indicates an initialtransmission or a retransmission, i=0 indicates an initial transmission,i>0 indicates a retransmission, and i is an integer. For example, i=1indicates the first retransmission, i=2 indicates the secondretransmission, and so on. An upper limit of retransmissions depends ona maximum retransmission times of the system. An output bit sequence foreach initial transmission or retransmission may be a redundancy versionof the coded block. k₀(i) indicates a starting position of an output bitsequence for the i^(th) transmission in the coded block of the circularbuffer, which may also be referred to as a starting position of aredundancy version rv(i) for the i^(th) retransmission.

402: Determine the output bit sequence in a circular buffer based on alength E(i) of the output bit sequence and the starting position k₀(i).

The communications device 30 may determine the output bit sequence basedon the length E(i) of the output bit sequence for the i^(th)transmission and the starting position k₀(i) obtained in step 401. Forexample, the communications device 30 sequentially obtains E(i) bitsstarting from a (k₀(i)^(th) bit of the coded block as the output bitsequence. The output bit sequence does not include any filler bit;therefore, if the communications device 30 obtains, as the output bitsequence, the E(i) bits in F(i) bits starting from the (k₀(i))^(th) bitof the coded block, a quantity of filler bits is F(i)−E(i). Therefore,an end location of the output bit sequence is k₀(i)+F(i). F(i) is a bitquantity required for sequentially obtaining the E(i) output bits fromthe coded block starting from k₀(i). F(i) is an integer greater than orequal to 0.

For example, after sending an output bit sequence for the initialtransmission, namely, a 0^(th) transmission, the communications device30 receives a negative acknowledgement NACK from the communicationsdevice 31. The communications device 30 needs to determine a startingposition k₀(1) of an output bit sequence for the 1^(st) transmission,namely, the 1^(st) redundancy version rv(1). Therefore, thecommunications device obtains the starting position k₀(1) of the outputbit sequence in the coded block stored in the circular buffer, anddetermines the output bit sequence for the 1^(st) transmission, namely,the redundancy version rv(1), based on a length E(1) of the output bitsequence and the starting position k₀(1). The communications device 30sends the output bit sequence rv(1) to the communications device 31. Ifthe communications device 30 receives the NACK from the communicationsdevice 31, the communications device 30 needs to determine a startingposition k₀(2) of an output bit sequence for the 2^(nd) transmission,namely, the 2^(nd) redundancy version rv(2), and determine the outputbit sequence for the 2^(nd) transmission based on a length E(2) of theoutput bit sequence and the starting position k₀(2), that is, determinethe redundancy version rv(2). The rest can be deduced by analogy. Thecommunications device may end the retransmission of the coded blockuntil the maximum retransmission is reached or the communications device30 receives a positive acknowledgement ACK from the communicationsdevice 31. Certainly, the communications device 30 may perform aplurality of retransmissions without considering the NACK or the ACKfrom the communications device 31.

During decoding, the communications device 31 at a receive end needs toperform combining and decoding on soft channel bits received in theinitial transmission and soft channel bits of redundancy versions. For acoded block obtained through LDPC coding, a quantity of repeated bits orskipped bits between the redundancy versions needs to be reduced toimprove decoding performance of the communications device at the receiveend.

An LDPC coded block shown in FIG. 5-1 is used as an example. It isassumed that a code rate of a kernel matrix of the LDPC coded blockbefore puncturing is 0.89, and a lowest code rate supported by the LDPCcoded block is 0.33. The LDPC coded block includes information bits andredundancy bits. The information bits include systematic to-be-puncturedbits and information bits that cannot be punctured. The redundancy bitsinclude parity bits that correspond to weight-2 columns and that cannotbe punctured, parity bits that correspond to weight-2 columns and thatcan be punctured, and parity bits that correspond to weight-1 columnsand that can be punctured. Puncturing may also indicate not sending. Apunctured bit is a bit not to be sent, and a bit that cannot bepunctured means that the bit needs to be sent. The parity bitscorresponding to weight-2 columns correspond to a column in a bidiagonalstructure part in a parity check matrix, or in other words, correspondto a column in a bidiagonal structure part in a kernel matrix. An outputbit sequence e₀ including the information bits that are not puncturedand the parity bits that correspond to weight-2 columns and that are notpunctured has a highest code rate.

There are a plurality of sizes affecting decoding performance of theLDPC code. For example, during decoding of the LDPC code, a redundancypart other than the information bits usually needs to be selected in anencoding order to form a code word for decoding. For another example,for the LDPC code, parity bits corresponding to weight-2 columns arepunctured to obtain a code rate higher than an original code ratesupported by the kernel matrix. During retransmission, the puncturedparity bits corresponding to weight-2 columns need to be retransmittedfirst, and then punctured parity bits in a weight-1 column part aresent. For another example, during retransmission, a higher proportion ofrepeated redundancy bits indicates poorer decoding performance.

As shown in FIG. 5-2 , there are four starting position values p₀, p₁,p₂, and p₃. In the initial transmission, an output bit sequence, namely,a redundancy version 0, is obtained starting from the 0^(th) startingposition p₀. In the 1^(st) retransmission, an output bit sequence,namely, a redundancy version 1, is obtained starting from the 1^(st)starting position p₁. The redundancy version 0 and the redundancyversion 1 are not continuous. A large quantity of skipped bits are nottransmitted, and especially parity bits corresponding to weight-2columns are not selected. After receiving the two redundancy versions,the communications device at the receive end performs combining anddecoding. However, because redundant bits skipped in FIG. 5-2 are nottransmitted to the communications device at the receive end, theredundant bits cannot be selected prior to redundant bits in theredundancy version 1 to form a code word for decoding. Consequently,decoding performance is greatly lowered. In addition, the skipped bitsin FIG. 5-2 also include punctured parity bits corresponding to weight-2columns, further degrading the decoding performance.

As shown in FIG. 5-3 , in the initial transmission, an output bitsequence, namely, a redundancy version 0, is obtained starting from the0^(th) starting position p₀. In the 1^(st) retransmission, an output bitsequence, namely, a redundancy version 1, is obtained starting from the1^(st) starting position p₁. Although the redundancy version 0 and theredundancy version 1 are continuous, if a code rate of the initialtransmission is relatively low, there are a relatively large quantity ofrepeated bits, leading to a loss of the decoding performance.

In step 401, a value of k₀(i) may be p_(k), and p_(k) is one of {p₀, p₁,p₂ . . . , p_(k) _(max) ⁻¹}. In other words, there are k_(max) startingposition values. 0≤p_(k)<N_(CB), p_(k) is an integer, k is an integer,0≤k<k_(max), N_(CB) is a size of the coded block, and k_(max) is aninteger greater than or equal to 4. For example, k_(max)=2^(n), and n isan integer greater than or equal to 2; or k_(max)=Nb, and Nb is aquantity of columns of a base matrix.

The subscript k in p_(k) may be a redundancy version starting positionnumber rv_(idx).

{p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} may be defined in a plurality ofmanners. For example, the set may be a set including only elements p₀,p₁, p₂ . . . , p_(k) _(max) ⁻¹, or may be a subset of another set. Theelements in the set {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} may be arrangedin a particular order, or may not be arranged in a particular order.This is not specifically limited in this application.

In a first possible implementation, the k_(max) values {p₀, p₁, p₂ . . ., p_(k) _(max) ⁻¹} may be evenly distributed based on differences. Adifference between two values a and b may be represented by |α−b|, and ∥represents calculating an absolute value. For the value of the startingposition of the coded block in the circular buffer, if p_(k)≥p_(k−1), adifference between p_(k) and p_(k−1) is |p_(k)−P_(k)−P_(k−1)|; and ifp_(k)<p_(k−1), the difference between p_(k) and p_(k−1) is|(p_(k)+N_(CB))−p_(k−1)|. For example, the difference is an integer S. Adifference between two adjacent values is S. If k>0, p_(k) may beobtained based on a previous value p_(k−1). For example, p_(k) satisfiesP_(k)=(P_(k−1)+S) mod N_(CB). Alternatively, p_(k) may be obtained basedon p₀, and p_(k) satisfies p_(k)=(p₀+k·S) mod N_(CB). p₀ may be aninteger multiple of a lifting size, and p₀=l·z, where l is an integer,and 0≤l<Nb. If p₀=0, the equation may be simplified as that p_(k)satisfies p_(k)=(k·S) mod N_(CB).

The k_(max) values {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} may be set basedon the size N_(CB) of the coded block. S may be

$\left\lfloor \frac{N_{CB}}{k_{\max}} \right\rfloor\mspace{14mu}{or}\mspace{14mu}{\left\lceil \frac{N_{CB}}{k_{\max}} \right\rceil.}$In this case, if k>0, p_(k) satisfies

$p_{k} = {\left( {p_{k - 1} + \left\lfloor \frac{N_{CB}}{k_{\max}} \right\rfloor} \right){mod}\mspace{14mu} N_{CB}}$$p_{k} = {\left( {p_{k - 1} + \left\lceil \frac{N_{CB}}{k_{\max}} \right\rceil} \right){mod}\mspace{14mu}{N_{CB}.}}$or For another example, p_(k) satisfies

${p_{k} = {\left( {p_{0} + \left\lfloor \frac{N_{CB} \cdot k}{k_{\max}} \right\rfloor} \right){mod}\mspace{14mu} N_{CB}}},{p_{k} = {\left( {p_{0} + \left\lceil \frac{N_{CB} \cdot k}{k_{\max}} \right\rceil} \right){mod}\mspace{14mu} N_{CB}}},{p_{k} = {\left( {p_{0} + {k \cdot \left\lfloor \frac{N_{CB}}{k_{\max}} \right\rfloor}} \right){mod}\mspace{14mu} N_{CB}}},{{{or}\mspace{14mu} p_{k}} = {\left( {p_{0} + {k \cdot \left\lceil \frac{N_{CB}}{k_{\max}} \right\rceil}} \right){mod}\mspace{14mu}{N_{CB}.}}}$

┌ ┐ represents rounding up to an integer, and └ ┘ represents roundingdown to an integer. For example, 2.1 is rounded up to 3, and is roundeddown to 2.

In an example in which the coded block has a length of 215 bits, k_(max)is 8, and the difference between adjacent values is

${\left\lfloor \frac{215}{8} \right\rfloor = {26\mspace{14mu}{bits}}},$if p₀=0, values in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} satisfy

${p_{k} = {\left\lfloor \frac{N_{CB} \cdot k}{k_{\max}} \right\rfloor{mod}\mspace{14mu} N_{CB}}},$and are {0, 26, 52, 78, 104, 130, 156, 182}. It may be learned that inthe example, the elements in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} may bedistributed in ascending order at equal intervals. It should be notedthat this is merely an example for description herein, and thisapplication is not limited thereto. For example, the elements in {p₀,p₁, p₂ . . . , p_(k) _(max) ⁻¹} may also be arranged in descendingorder, and the difference between the adjacent elements may also haveother values.

For another example, k_(max)=Nb, and Nb is a quantity of columns of thebase matrix. N_(CB) is obtained based on Nb·z and optionally throughpuncturing. Therefore, the difference between the adjacent values may bez. For any value p_(k), P_(k)=(k·z) mod N_(CB). For example, if Nb=50and z=4, the values in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} satisfyp_(k)=(k·z) mod N_(CB), and are {0, 4, 8, . . . , 196}. It should benoted that this is merely an example for description herein, and thisapplication is not limited thereto.

An increase in k_(max) can reduce a distance between the startingpositions of the redundancy versions. The redundancy version determinedbased on the starting position can also improve decoding performance ofthe communications device at the receive end. For example, k_(max) maybe an integer greater than 4. For example, k_(max)=5; or k_(max)=2^(n),and k_(max) is 8 or above, for example, 8 or 16, where n is an integergreater than 2. For another example, k_(max)=Nb, and Nb is the quantityof columns of the base matrix of the coded block. This is merely anexample for description herein, and this application is not limitedthereto.

In the foregoing method, an interval between redundancy versiontransmissions does not vary greatly or does not include a large quantityof repeated bit. Therefore, the foregoing method can adapt to variousinitial transmission code rates, and has relatively stable performance.

In a second possible implementation, the k_(max) values {p₀, p₁, p₂ . .. , p_(k) _(max) ⁻¹} may alternatively be set in a manner thatdifferences between adjacent values are varied.

For example, p_(m+) is used as a demarcation point, k_(max) m−2 valuesafter p_(m+1) may be set in a manner in which differences betweenadjacent values are in ascending order, as described in the above,k_(max) is an integer greater than or equal to 4. For example,p_(m+2)−p_(m+1)≤p_(m+3)−p_(m+2). The m+1 value(s) between p₀ and p_(m+1)may be evenly distributed based on a difference, which, for example, hasa value of

${\left\lfloor \frac{p_{m + 1} - p_{0}}{m + 1} \right\rfloor\mspace{14mu}{or}\mspace{14mu}\left\lceil \frac{p_{m + 1} - p_{0}}{m + 1} \right\rceil};$or may be set in another manner in which differences between adjacentvalues are varied. This is not limited herein. For example, ifk_(max)=4, according to P_(m+2)−P_(m+1)≤P_(m+3)−P_(m+2) and thesubscript m+3 of P_(m+3) is less than or equal to k_(max−1), that ism+3≤3, thus m=0, therefore p₂−p₁≤p₃−p₂. Understandably, for a manner inwhich differences between adjacent values are varied, p₂−p₁<p₃−p₂, for amanner in which differences between adjacent values are even,p₂−p₁=p₃−p₂.

For example, during initial transmission, an output bit sequence havinga high code rate is obtained, and includes information bits and paritybits that correspond to weight-2 columns and that are not punctured, forexample, e₀ in FIG. 5-1 . A length of the output bit sequence isE₀=(Nb−Mb+j)*z, where j is a quantity of parity bits corresponding toweight-2 columns or a quantity of parity bits that correspond toweight-2 columns and that are not punctured. A value of p_(m+1) may be(Nb−Mb+j)*z.

If p_(k)>(Nb−Mb+j)*z, p_(k) satisfies p_(k)−p_(k−1)≤p_(k+1)−p_(k) wherem+1<k<k_(max)−1. As described in the above, k_(max) is an integergreater than or equal to 4. If k_(max)=4, k_(max)−1=3, that is to saym+1<k<3, as k is an integer, thus k=2, m=0. Therefore p₂−p₁≤p₃−p₂.

If p_(k)<(Nb−Mb+j)*z, a difference between adjacent values in the m+1value(s) between p₀ and p_(m+1) is

$\left\lfloor \frac{p_{m + 1} - p_{0}}{m + 1} \right\rfloor\mspace{14mu}{or}\mspace{14mu}{\left\lceil \frac{p_{m + 1} - p_{0}}{m + 1} \right\rceil.}$For example, for k<m+1, p_(k) satisfies

$p_{k} = {{\left( {p_{0} + \left\lfloor \frac{\left( {p_{m + 1} - p_{0}} \right) \cdot k}{m + 1} \right\rfloor} \right){mod}\mspace{14mu} p_{m + 1}\mspace{14mu}{or}\mspace{14mu} p_{k}} = {\left( {p_{0} + \left\lceil \frac{\left( {p_{m + 1} - p_{0}} \right) \cdot k}{m + 1} \right\rceil} \right){mod}\mspace{14mu}{p_{m + 1}.}}}$

If p_(k)=(Nb−Mb+j)*z, that is, p_(k)=p_(m+1), and k=m+1.

According to the method, starting positions are more densely distributedat a position closer to information bits, and starting positions aremore sparsely distributed at a position closer to a last bit of thecoded block.

The base matrix shown in FIG. 1 is used as an example. Nb=38, Mb=13, andz=4. The last four columns in the kernel matrix Hk are a bidiagonalstructure part, to be specific, corresponding columns of parity bitscorresponding to weight-2 columns. Therefore, a quantity of the paritybits corresponding to weight-2 columns is four. If two columns are notpunctured, a quantity of parity bits that correspond to weight-2 columnsand that are not punctured is two. If j is a quantity of parity bitscorresponding to weight-2 columns, E_(r0)=116. If j is a quantity ofparity bits that correspond to weight-2 columns and that are notpunctured, E_(r0)=108. In an example in which j is the quantity ofparity bits that correspond to weight-2 columns and that are notpunctured, k_(max) is 8, and the coded block has a length of 152 bits,p₄=E_(r0)=108, p₀=2, and three values p₁, p₂, and p₃ exist between p₀and p₄. A difference between two adjacent values is

$\left\lfloor \frac{106}{4} \right\rfloor = 26.$Three values p₅, p₆, and p₇ exist between p₄ and the end bit of thecoded block, with differences between them being in decreasing order.The differences are sequentially 6, 10, and 14. The k_(max) values are{2, 28, 54, 80, 108, 114, 124, 138}. It should be noted that thedistribution of the elements in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} inascending order is merely an example herein. It may be understood thatthis application is not limited thereto, the elements in {p₀, p₁, p₂ . .. , p_(k) _(max) ⁻¹} may alternatively be distributed in descendingorder, and an interval between adjacent elements in {p₀, p₁, p₂ . . . ,p_(k) _(max) ⁻¹} may alternatively be another value.

For the value p_(k) in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} k₀(i) instep 401 may be obtained in a plurality of manners.

Based on the first implementation or the second implementation, in athird possible implementation, if i>0, the starting position k₀(i) isdetermined based on a starting position k₀(i−1) of a previoustransmission output bit sequence and a length E(i−1) of the previoustransmission output bit sequence.

For ease of description, a direction from a last position of theprevious transmission output bit sequence to the last bit (an(N_(CB−)1)^(th) bit) of the coded block is used as a front-to-enddirection, and a direction from the last position of the previoustransmission output bit sequence to a start bit (a 0^(th) bit) of thecoded block is used as an end-to-front direction.

For example, to reduce a quantity of repeated redundancy bits, thestarting position k₀(i) may be obtained in a front-to-end directionbased on the starting position k₀(i−1) of the previous transmissionoutput bit sequence and the length E(i−1) of the previous transmissionoutput bit sequence. The output bit sequence does not include any fillerbit; therefore, if F(i−1) is a bit quantity required for sequentiallyobtaining the E(i−1) output bits from the coded block starting fromk₀(i−1), the last position of the previous obtained output bit sequenceis (k₀(i−1)+F(i−1)−1) mod N_(CB). A value p_(k) of a first startingposition in the front-to-end direction from the last position of theprevious obtained output bit sequence is used as k₀(i). If the lastposition of the previous obtained output bit sequence is greater than alargest value in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹}, p_(k) is asmallest value in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹}.

It may be learned that p_(k) is a minimum value satisfyingP_(k)≥((k₀(i−1)+F(i−1)) mod N_(CB)). If no value in {p₀, p₁, p₂ . . . ,p_(k) _(max) ⁻¹} satisfies P_(k)≥((k₀(i−1)+F(i−1)) mod N_(CB)), in otherwords, ((k₀(i−1)+F(i−1)) mod N_(CB)) is greater than the largest valuein {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹}, p_(k) is the smallest value in{p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹}.

The values {2, 28, 54, 80, 108, 114, 124, 138} in the foregoingimplementation are used as an example. The starting position k₀(i−1) ofthe previous transmission output bit sequence is 2, and the lengthE(i−1) of the previous transmission output bit sequence is 25 bits.There are 5 filler bits; therefore, the bit quantity F(i−1) required forsequentially obtaining the E(i−1) output bits from the coded blockstarting from k₀(i−1) last time is 30. For the output bit sequence k₀(i)for the i^(th) transmission, k₀(i)=54 if the method of obtaining thestarting position in a front-to-end direction in this embodiment isused. If the starting position k₀(i−1) of the previous transmissionoutput bit sequence is 124, the length E(i−1) of the previoustransmission output bit sequence is 30 bits, and there are no fillerbits, the bit quantity required for sequentially obtaining the E(i−1)output bits from the coded block starting from k₀(i−1) last time is 30,and k₀(i)=2. It should be noted that this is merely an example herein,and this application is not limited thereto.

For another example, to meet a requirement of sequential decoding, thestarting position k₀(i) is obtained in an end-to-front direction basedon the starting position k₀(i−1) of the previous transmission output bitsequence and the length E(i−1) of the previous transmission output bitsequence. The output bit sequence does not include any filler bit;therefore, if F(i−1) is a bit quantity required for sequentiallyobtaining E(i−1) output bits from the coded block starting from k₀(i−1),the last position of the previous obtained output bit sequence is(k₀(i−1)+F(i−1)−1) mod N_(CB). A value p_(k) of the first startingposition in the end-to-front direction from the last position of theprevious obtained output bit sequence is used as k₀(i). If the endlocation of the previous obtained output bit sequence is less than asmallest value in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹}, p_(k) is alargest value in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹}. It may be learnedthat p_(k) is a maximum value satisfying p_(k)≤((k₀(i−1)+F (i−1)) modN_(CB)). If no value in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} satisfiesp_(k) ((k₀(i−1)+F (i−1)) mod N_(CB)), in other words, ((k₀(i−1)+F(i 1))mod N_(CB)) is less than the smallest value in {p₀, p₁, p₂ . . . , p_(k)_(max) ⁻¹} p_(k) is the largest value in {p₀, p₁, p₂ . . . , p_(k)_(max) ⁻¹}.

The values {2, 28, 54, 80, 108, 114, 124, 138} in the foregoingembodiment and that the length of the coded block is 152 bits are stillused as an example. The starting position k₀(i−1) of the previoustransmission output bit sequence is 2, and the length E(i−1) of theprevious transmission output bit sequence is 25 bits. There are 5 fillerbits. Therefore, the bit quantity F(i−1) required for sequentiallyobtaining the E(i−1) output bits from the coded block starting fromk₀(i−1) last time is 30. For the output bit sequence k₀(i) for thetransmission, k₀(i)=28 if the method of obtaining the starting positionin an end-to-front direction is used. If the starting position k₀(i−1)of the previous transmission output bit sequence is 124, the lengthE(i−1) of the previous transmission output bit sequence is 20 bits, andthere are nine filler bits, the bit quantity F(i−1) required forsequentially obtaining the E(i−1) output bits from the coded blockstarting from k₀(i−1) last time is 29, and k₀(i)=138. It should be notedthat this is merely an example herein, and this application is notlimited thereto.

For another example, to compensate decoding performance losses caused byrepeating bits and by skipping redundancy bits, with reference toresults of obtaining k₀(i) in an end-to-front direction and obtainingk₀(i) in a front-to-end direction in the foregoing two examples, a valueof one of the two results that has a smaller difference with the endlocation of the previous obtained output bit sequence is used as k₀(i).If p₀≤((k₀(i−1)+F (i−1)) mod N_(CB))≤p_(k) _(max) ⁻¹, p_(k) is a valuein {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} that has a smallest differencewith ((k₀ (i−1)+F (i−1)) mod N_(CB)); or if ((k₀ (i−1)+F (i−1)) modN_(CB)) is less than a smallest value in {p₀, p₁, p₂ . . . , p_(k)_(max) ⁻¹} or ((k₀ (i−1)+F (i−1)) mod N_(CB)) is greater than a largestvalue in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} p_(k) is one of thesmallest value in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} and the largestvalue p_(k) _(max) ⁻¹ in {p₀, p₁, p₂ . . . , p_(k) _(max) ⁻¹} that has asmaller difference with ((k₀ (i−1)+F (i−1)) mod N_(CB)). In a possibleimplementation, P_(k+) and p_(k−) may be determined first. p_(k+), is avalue of the first starting position in the front-to-end direction fromthe last position of the previous obtained output bit sequence, p_(k−)is a value of the first starting position in the end-to-front directionfrom the last position of the previous obtained output bit sequence, andp_(k) is one of p_(k+) and p_(k−) has a smaller difference with ((k₀(i−1)+F (i−1)) mod N_(CB)). If a difference between p_(k+) and((k₀(i−1)+F (i−1)) mod N_(CB)) is equal to that between p_(k−) and((k₀(i−1)+F (i−1)) mod N_(CB)), p_(k) may be selected from the twoarbitrarily or based on a value determining direction.

The values {2, 28, 54, 80, 108, 114, 124, 138} in the foregoingembodiment and that the length of the coded block is 152 bits are stillused as an example. The starting position k₀(i−1) of the previoustransmission output bit sequence is 2, and the length E(i−1) of theprevious transmission output bit sequence is 26 bits. The bit quantityF(i−1) required for sequentially obtaining the E(i−1) output bits fromthe coded block starting from k₀(i−1) last time is 30. For the outputbit sequence k₀(i) for the i^(th) transmission, k₀(i)=28 if the methodin this embodiment is used to obtain the starting position. If k₀(i−1)is 124 bits, the length E(i−1) of the previous transmission output bitsequence is 29 bits, and the bit quantity F(i−1) required forsequentially obtaining the E(i−1) output bits from the coded blockstarting from k₀(i−1) last time is 30, a value obtained in thefront-to-end direction is p₀=2, a difference between P₀ and ((k₀ (i−1)+F(i−1)) mod N_(CB)) is 1, a value obtained in the end-to-front directionis p₇=138, and a difference between p₇ and ((k₀ (i−1)+F (i−1)) modN_(CB)) is 15. Therefore, k₀(i)=p₀=2. It should be noted that this ismerely an example herein, and this application is not limited thereto.

For another example, to compensate decoding performance losses caused byrepeating bits and by skipping redundancy bits, a direction forobtaining the starting position k₀(i) in the i^(th) transmission isdetermined based on a correspondence between a quantity i oftransmissions and the direction for obtaining the starting positionk₀(i), and the starting position k₀(i) is obtained based on the lastposition of the previous transmission output bit sequence and thedetermined direction for obtaining the starting position k₀(i). A tableof the quantity i of transmissions and the direction for obtaining thestarting position k₀(i), for example, Table 1, may be set in thecommunications device. A largest quantity of retransmissions is three,and no obtaining direction needs to be set for the initial transmission.

TABLE 1 Quantity of transmissions Obtaining direction 1 front-to-end 2end-to-front 3 end-to-front

The values {2, 28, 54, 80, 108, 114, 124, 138} in the foregoingembodiment and that the length of the coded block is 152 bits are stillused as an example. If a starting position k₀(0) of an output bitsequence for the initial transmission is 2, a length E(0) of the outputbit sequence for the initial transmission is 20 bits, and a quantity offiller bits is 10, F(0)=30 bits. It is assumed that there are a samequantity of filler bits each time when an output bit sequence isobtained, an output bit sequence for each transmission has a samelength, and the starting position is obtained by using thecorrespondence in Table 1 above. For an output bit sequence for the1^(st) transmission, a starting position k₀(1) is obtained in afront-to-end direction, and k₀(1)=54. For an output bit sequence for the2nd transmission, a starting position k₀(2) is obtained in anend-to-front direction, and k₀(2)=80. For an output bit sequence for the3^(rd) transmission, a starting position k₀(3) is obtained, andk₀(3)=108. It should be noted that this is merely an example herein, andthis application is not limited thereto.

“End-to-front” and “front-to-end” in the obtaining directions may beindicated by using particular numerical values, and are not limited to aliteral expression manner. For example, 0 represents “end-to-front”, and1 represents “front-to-end”; or another numerical expression manner isused. The correspondence between the quantity i of transmissions and thedirection for obtaining the starting position k₀(i) may alternatively bedefined in another form. This embodiment of the present invention is notlimited thereto.

The direction for obtaining the starting position of the output bitsequence for the i^(th) transmission may be determined based on thequantity i of transmissions. The starting position k₀(i) is obtained inan end-to-front direction based on the direction for obtaining thestarting position of the output bit sequence for the i^(th)transmission, the starting position k₀(i−1) of the previous transmissionoutput bit sequence, and the length E(i−1) of the previous transmissionoutput bit sequence.

Based on the first implementation or the second implementation, in afourth possible implementation, an order in which the starting positionis obtained during each transmission may be defined, and a valueselection order of the subscript k in p_(k) during each transmission mayalso be defined. The order may be indicated to the communications deviceat the receive end, or may be prestored in the communications device atthe transmit end and the communications device at the receive end.

The subscript k in p_(k) may be a redundancy version starting positionnumber rv_(idx), a redundancy version starting position number in thei^(th) transmission may be represented as rv_(idx)(i), and the startingposition k₀(i) may be determined based on the redundancy versionstarting position number rv_(idx)(i mod k_(max)).

A starting position obtaining method based on a fixed order may be used.In an embodiment, a value selection order of rv_(idx) may be defined. Aquantity of values in the value selection order may be k_(max), or maybe a largest quantity R_(max) of retransmissions. For example, whenk_(max)=8, the value selection order of rv_(idx) is sequentially 0, 3,6, 2, 5, 7, 4, and 1. For the initial transmission, an output bitsequence is determined starting from the p₀ ^(th) bit. For the firsttransmission, k₀(1)=p₃, and an output bit sequence is determinedstarting from the p₀ ^(th) bit. For the second transmission, k₀(2)=p₆,and the output bit sequence is determined starting from the p₆ ^(th)bit. The rest can be deduced by analogy. For the k_(max) ^(th)transmission, the output bit sequence is determined starting from thep^(th) bit again. To be specific, for the i^(th) transmission,k=rv_(idx)(i mod k_(max)), and k₀(i)=p_(k). For another example, themaximum quantity R_(max) of retransmissions is 3, and a value selectionorder set of rv_(idx) is {0, 2, 3, 1}. In this case, for the initialtransmission, and the output bit sequence is determined starting fromthe p₀ ^(th) bit. For the 1st transmission, k₀(1)=p₂, and the output bitsequence is determined starting from the p₃ ^(th) bit. For the 2^(nd)transmission, k₀(2) is p₃. For the i^(th) transmission, k=rv_(idx)(i modR_(max)), and k₀(i)=P_(k).

Further, the value selection order of rv_(idx) may also be determinedbased on a value of an initial transmission code rate, or may bedetermined based on a length E of an output bit sequence for eachtransmission and a lifting size z. In a non-adaptive retransmissionscenario, a length of an output bit sequence in the initial transmissionis equal to that of an output bit sequence in the retransmission. Forexample, the value selection order of rv_(idx) is determined based on

$\left\lceil \frac{E}{z} \right\rceil.$

For example, k_(max)=8, and a 66*82 LDPC matrix is used. A quantity ofcolumns of information bits is 16. For the coded block, for acorrespondence between the value selection order of rv_(idx) and thecode rate of the initial transmission, refer to Table 2. For example,R₀≥0.8, and the value selection order of rv_(idx) is {0, 2, 4, 6}.

TABLE 2 Initial transmission code rate R₀ Value selection order ofrv_(idx)      R₀ ≥ 0.8 0, 2, 4, 6 0.53 ≤ R₀ < 0.8 0, 3, 6, 2       R₀ <0.53 0, 4, 2, 6

For another example, k_(max)=8, and a 66*82 LDPC matrix is used. Aquantity of columns of information bits is 16. For the coded block,refer to Table 3 for a correspondence between the value selection orderof rv_(idx) and the initial transmission code rate. For example,

${20 < \left\lceil \frac{E}{z} \right\rceil \leq 30},$and the value selection order of rv_(idx) is {0, 3, 6, 2}.

TABLE 3 Length E of output bit sequence and lifting Value selection sizez order of rv_(idx) $\left\lceil \frac{E}{z} \right\rceil \leq 20$ 0, 2,4, 6 $20 < \left\lceil \frac{E}{z} \right\rceil \leq 30$ 0, 3, 6, 2$\left\lceil \frac{E}{z} \right\rceil > 30$ 0, 4, 2, 6

This manner is suitable for non-adaptive retransmission, and informationabout the starting position does not need to be indicated to thecommunications device at the receive end before each time of sending.

The starting position k₀(i) of the output bit sequence in the codedblock may alternatively be obtained based on rv_(idx) indicated by thecommunications device at the transmit end. This manner is suitable foradaptive retransmission.

In a fifth possible implementation, for a retransmission, to bespecific, for i>0, the output bit sequence for the i^(th) transmissionand an output bit sequence for the (i−1)^(th) transmission are connectedend to end. In this implementation, k₀(i) is determined based on astarting position k₀(i−1) of a previous transmission output bit sequenceand a length E(i−1) of the previous transmission output bit sequence.The output bit sequence does not include any filler bit. Therefore,F(i−1) may be obtained based on k₀(i−1) and E(i−1). F(i−1) is a bitquantity required for sequentially obtaining E(i−1) output bits from thecoded block starting from k₀(i−1). k₀(i)=(k₀(i−1)+F(i−1)) mod N_(CB). Inthis implementation, output bit sequences of two adjacent transmissionsare consecutive, and no repeated bit exists between the two output bitsequences, so that when such output bit sequences are sent to thecommunications device at the receive end, relatively good decodingperformance can be achieved.

Further, based on the retransmission manner with end-to-end connection,after all bits of the coded block have been transmitted once, an offsetE_(offset) is added for each retransmission, to be specific,k₀(i)=(k₀(i−1)+F (i−1)+E_(offset)) mod N_(CB). In this implementation,if the end bit of the coded block is already transmitted, k₀(i)=(k₀(i−1)+F (i−1)+E_(offset)) mod N_(CB); otherwise,k₀(i)=(k₀(i−1)+F(i−1)) mod N_(CB). In this way, after all the bits aretransmitted, an offset is added for each retransmission, so that aquantity of repeated bits is reduced, thereby reducing a decodingperformance loss.

Optionally, after the method for processing information is performed,the communications device may further process the output bit sequence,so that the output bit sequence is used during sending or receiving. Forexample, the processing includes interleaving the output bit sequence,mapping the output bit sequence to modulation symbols, and the like. Forthe processing, refer to a corresponding processing method in the priorart, and details are not described herein.

FIG. 6 is a flowchart of a method for processing information accordingto an embodiment of the present invention. The method may be applied toa communications system. The communications system includes acommunications device 30 and a communications device 31. The method maybe implemented by the communications device 31 and includes thefollowing steps.

601: Obtain a starting position k₀(i) of a soft bit sequence having alength of E(i) stored in a soft buffer.

602: Combine and store the soft bit sequence in step 601 in the softbuffer starting from the starting position k₀(i).

The communications device 30 sends the output bit sequence obtained inthe foregoing embodiments to the communications device 31. It may beunderstood that the output bit sequence in the foregoing embodiments isan output bit sequence obtained after rate matching, the communicationsdevice 30 may perform processing such as interleaving and modulation onthe output bit sequence obtained after the rate matching and send asignal corresponding to the output bit sequence, and the communicationsdevice 31 receives the output signal and performs demodulation andde-interleaving on the output signal, to obtain a soft bit sequencecorresponding to the output bit sequence. To be specific, one bit in theoutput bit sequence corresponds to one soft channel bit (soft channelbit) in the soft bit sequence. Positions of the soft channel bits storedin the soft buffer of the communications device 31 are in a one-to-onecorrespondence with positions in the coded block in the circular bufferof the communications device 30. A size of the soft buffer and a size ofthe coded block in the circular buffer are also the same and may beN_(CB).

For example, an output bit sent by the communications device 30 is 1,and after channel transmission, the communications device 31 obtains asoft channel bit corresponding to the output bit, where the soft channelbit is 1.45. If a position of the output bit in the coded block is the5^(th) bit, the 5^(th) soft channel bit in the soft buffer of thecommunications device 31 is 1.45. It should be noted that this is merelyan example for description herein, and this embodiment of the presentinvention is not limited thereto. If the output bit sequence obtained bythe communications device 30 includes nc output bits, the communicationsdevice 31 may obtain nc corresponding soft channel bits. If receivingsoft channel bits of a same position at two times, the communicationsdevice 31 combines the two soft values. For example, if a soft channelbit received in the 1st transmission is 1.45 and a soft channel bitreceived in the 2^(nd) transmission is 0.5, 1.95 is obtained aftercombining. It should be noted that this is merely an example herein, andthis application is not limited thereto.

It may be learned that the starting position k₀(i) and the obtainingmanner thereof have features corresponding to the foregoing embodiments.Refer to the descriptions in the foregoing embodiments, and details arenot described herein again. It should be noted that in thecommunications device 30, the starting position is relative to the codedblock in the circular buffer; in the communications device 31, thestarting position is relative to the soft buffer; on a side of thecommunications device 30, the output bit sequence is determined in thecoded block in the circular buffer, and on a side of the communicationsdevice 31, the received soft bit sequence are stored in the soft buffer.

FIG. 7 is a schematic structural diagram of an apparatus 700 forprocessing information. The apparatus may be applied to thecommunications device 30 in the communications system shown in FIG. 3 .The apparatus 700 may also be referred to as a rate matching apparatus.The apparatus 700 may be configured to implement the foregoing methodembodiments. Refer to the descriptions in the foregoing methodembodiments, and details are not described herein again.

The apparatus 700 may include an obtaining unit 701 and a processingunit 702.

The obtaining unit 701 is configured to obtain a starting position k₀(i)of an output bit sequence in a coded block. The processing unit 702 isconfigured to determine the output bit sequence in the coded block basedon a length E(i) of the output bit sequence and the starting positionk₀(i). The coded block is stored in a circular buffer, and i is aninteger greater than or equal to 0. For details about how to obtaink₀(i) and determine the output bit sequence based on E(i) and k₀(i),refer to the descriptions in the foregoing method embodiments

FIG. 8 is a schematic structural diagram of an apparatus 800 forprocessing information. The apparatus may be applied to thecommunications device 31 in the communications system shown in FIG. 3 .The apparatus 800 may also be referred to as a rate de-matchingapparatus. The apparatus 800 may be configured to implement theforegoing method embodiments. For details, refer to the descriptions inthe foregoing method embodiments. The apparatus 800 may include anobtaining unit 801 and a processing unit 802.

The obtaining unit 801 is configured to obtain a starting position k₀(i)of a soft bit sequence having a length of E(i) stored in a soft buffer.The processing unit 802 is configured to combine and store the soft bitsequence obtained by the obtaining unit 801 in the soft buffer startingfrom the starting position k₀(i).

FIG. 9 is a schematic structural diagram of a communications device. Thecommunications device may be applied to the communications system shownin FIG. 3 . The communications device 30 may include an encoder 301, arate matcher 302, and a transceiver 303. The encoder 301 may also bereferred to as an encoding unit, an encoding circuit, or the like, andis mainly configured to encode information data. The rate matcher 302may also be referred to as a rate matching unit, a rate matchingcircuit, or the like, is mainly configured to determine, based on acoded block obtained by the encoder 301 by encoding, an output bitsequence to be sent, for example, configured to determine the output bitsequence in the foregoing embodiments, and may include, for example, theapparatus 700 in FIG. 7 . The transceiver 303 may also be referred to asa transceiver unit, a transceiver, a transceiver circuit, or the like,and is mainly configured to receive and send radio frequency signals,for example, configured to send the output bit sequence in the foregoingembodiments to the communications device 31. The communications device30 may further include other components, such as a component configuredto generate a transport block CRC, a component configured to performcode block segmentation and CRC check, an interleaver, and a modulator,which can be respectively configured to implement functions of parts ofthe communications device 30 in FIG. 3 .

It should be noted that the communications device 30 may include one ormore memories and one or more processors. The memory storesinstructions. The processor is coupled to the memory, to execute theinstructions in the memory to perform steps described in the methodembodiments. The memory may further include other instructions for theprocessor to execute to perform functions of other parts of thecommunications device 30, for example, code block segmentation, CRCcheck, interleaving, and modulation.

FIG. 10 is a schematic structural diagram of a communications device.The communications device may be applied to the communications systemshown in FIG. 3 . The communications device 31 may include a decoder311, a rate de-matcher 312, and a transceiver 313. The rate de-matcher312 may also be referred to as a rate de-matching unit or a ratede-matching circuit, may be configured to combine soft channel bits, forexample, configured to combine and store the soft channel bits of theoutput bit sequence in the foregoing embodiments in a soft buffer, andmay include, for example, the apparatus 800 in FIG. 8 . The decoder 311may also be referred to as a decoding unit or a decoding circuit, and ismainly configured to decode a received signal, for example, configuredto decode a soft channel bit in the soft buffer. The transceiver 313 mayalso be referred to as a transceiver unit, a transceiver, a transceivercircuit, or the like, and is mainly configured to receive and send radiofrequency signals, for example, configured to receive the output bitsequence in the foregoing embodiments that is sent by the communicationsdevice 30. The communications device 31 may further include othercomponents, such as a component configured to perform CRC check on atransport block, a component configured to perform code blockconcatenation, a deinterleaver, and a demodulator, which can berespectively configured to implement functions of parts of thecommunications device 31 in FIG. 3 .

It should be noted that the communications device 31 may include one ormore memories and processors, to implement the functions of the parts ofthe communications device 31 in FIG. 3 . A dedicated memory andprocessor may be disposed for each component. Alternatively, a pluralityof components share a same memory and processor.

It should be noted that the communications device 31 may include one ormore memories and one or more processors. The memory storesinstructions. The processor is coupled to the memory, to execute theinstruction in the memory to perform steps described in the methodembodiments. The memory may further include other instructions for theprocessor to execute to perform functions of other parts of thecommunications device 30, for example, code block concatenation,deinterleaving, and demodulation.

A person skilled in the art may further understand that variousillustrative logical blocks (illustrative logic block) and steps (step)that are listed in the embodiments of the present invention may beimplemented by using electronic hardware, computer software, or acombination thereof. Whether the functions are implemented by usinghardware or software depends on particular applications and a designrequirement of the entire system. A person skilled in the art may usevarious methods to implement the functions for each particularapplication, but such an implementation should not be construed as goingbeyond the scope of the embodiments of the present invention.

The various illustrative logical units and circuits described in theembodiments of the present invention may implement or operate thedescribed functions by using a design of a general purpose processor, adigital signal processor, an application-specific integrated circuit(ASIC), a field programmable gate array (FPGA) or another programmablelogical apparatus, a discrete gate or transistor logic, a discretehardware component, or any combination thereof. The general purposeprocessor may be a microprocessor. Optionally, the general purposeprocessor may also be any conventional processor, controller,microcontroller, or state machine. The processor may also be implementedby a combination of computing apparatuses, for example, a digital signalprocessor and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a digital signal processorcore, or any other similar configuration.

Steps of the methods or algorithms described in the embodiments of thepresent invention may be directly embedded in hardware, in instructionsexecuted by a processor, or in a combination thereof. The memory may bea RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROMmemory, a register, a hard disk, a removable hard disk, a CD-ROM, or anyother form of storage medium in the art. For example, the memory may beconnected to the processor so that the processor may read informationfrom the memory and write information to the memory. Optionally, thememory may be further integrated into a processor. The processor and thememory may be disposed in an ASIC, and the ASIC may be disposed in UE.Optionally, the processor and the memory may be disposed in differentcomponents of the UE.

With descriptions of the foregoing implementations, a person skilled inthe art may clearly understand that the present invention may beimplemented by hardware, firmware or a combination thereof. Whenimplemented by using a software program, the methods may be fully orpartially implemented in a form of a computer program product, and thecomputer program product includes one or more computer instructions.When the computer instructions are loaded and executed on the computer,the procedure or functions according to the embodiments of the presentinvention are all or partially generated. When the present invention isimplemented by using a software program, the foregoing functions may bestored in a computer readable medium or transmitted as one or moreinstructions or code in the computer readable medium. The computer maybe a general-purpose computer, a dedicated computer, a computer network,or other programmable apparatuses. The computer instructions may bestored in a computer readable storage medium, or may be transmitted froma computer readable storage medium to another computer readable storagemedium. The computer readable medium includes a computer storage mediumand a communications medium, where the communications medium includesany medium that cause a computer program to be transmitted from oneplace to another. The storage medium may be any available mediumaccessible to a computer. The following provides an example but does notimpose a limitation: The computer readable medium may include a RAM, aROM, an EEPROM, a CD-ROM, or another optical disc storage or a diskstorage medium, or another magnetic storage device, or any other mediumthat can be used to carry or store expected program code in a form ofinstructions or data structures and can be accessed by a computer. Inaddition, any connection may be appropriately defined as a computerreadable medium. For example, if software is transmitted from a website,a server or another remote source by using a coaxial cable, an opticalfiber/cable, a twisted pair, a digital subscriber line (DSL) or wirelesstechnologies such as infrared ray, radio and microwave, and the coaxialcable, optical fiber/cable, twisted pair, DSL or wireless technologiessuch as infrared ray, radio and microwave are included in a definitionof a medium to which they belong. For example, a disk (Disk) and disc(disc) used in the present invention includes a compact disc (CD), alaser disc, an optical disc, a digital versatile disc (DVD), a floppydisk and a Blu-ray disc, where the disk generally copies data by amagnetic means, and the disc copies data optically by a laser means. Theforegoing combination should also be included in the protection scope ofthe computer readable medium.

In conclusion, what is described above is merely example embodiments ofthe technical solutions of the present invention, but is not intended tolimit the protection scope of the present invention. Any modification,equivalent replacement, or improvement made without departing from theprinciple of the present invention shall fall within the protectionscope of the present invention.

What is claimed is:
 1. A method for performing rate matching in acommunications system, comprising: obtaining, by a communication device,a size N_(CB) of a coded block, wherein the coded block is obtainedbased on low-density parity-check (LDPC) code and stored in a circularbuffer; obtaining, by the communication device, a starting position ofan output bit sequence in the coded block, wherein a value of thestarting position is one of {p₀, p₁, p₂, p₃}, wherein p₀=0, p₁, p₂, andp₃ are integers based on the size N_(CB) of the coded block, wherein0<p₁<p₂<p₃≤N_(CB), and p₂−p₁<p₃−p₂; outputting, by the communicationdevice, the output bit sequence, wherein the output bit sequencecomprises a plurality of bits starting from the starting position in thecoded block; performing, by the communication device, interleaving onthe output bit sequence to generate an interleaved output bit sequence;generating, by the communication device, one or more modulation symbolsbased on the interleaved output bit sequence; and transmitting, by thecommunication device, a transmission signal comprising the one or moremodulation symbols.
 2. The method according to claim 1, furthercomprising: determining a length of the output bit sequence thatcomprises the plurality of bits.
 3. The method according to claim 1,wherein, during initial transmission, the output bit sequence includesinformation bits and parity bits that correspond to weight-2 columns. 4.The method according to claim 1, wherein the starting position isdetermined based on a redundancy version number.
 5. The method accordingto claim 4, wherein the redundancy version number is obtained throughsignaling.
 6. The method according to claim 4, wherein the redundancyversion number is obtained based on a sequence of redundancy versionnumbers and a value of i, wherein i is an integer greater than or equalto 0, the value of i indicates an i^(th) transmission.
 7. The methodaccording to claim 6, wherein the sequence of the redundancy versionnumbers is read from a memory, or the sequence of the redundancy versionnumbers is determined based on an initial transmission code rate.
 8. Anapparatus, comprising: at least one processor; and at least one memorycoupled to the at least one processor and storing instructions forexecution by the at least one processor, the instructions instruct theat least one processor to: obtain a size N_(CB) of a coded block,wherein the coded block is obtained based on low-density parity-check(LDPC) code and stored in a circular buffer; obtain a starting positionof an output bit sequence in the coded block, wherein a value of thestarting position is one of {p₀, p₁, p₂, p₃}, wherein p₀=0, p₁, p₂, andp₃ are integers based on the size N_(CB) of the coded block, wherein0<p₁<p₂<p₃≤N_(CB), and p₂−p₁<p₃−p₂; output the output bit sequence,wherein the output bit sequence comprises a plurality of bits startingfrom the starting position in the coded block; perform interleaving onthe output bit sequence to generate an interleaved output bit sequence;generate one or more modulation symbols based on the interleaved outputbit sequence; and transmit a transmission signal comprising the one ormore modulation symbols.
 9. The apparatus according to claim 8, whereinthe instructions further instruct the at least one processor todetermine a length of the output bit sequence that comprises theplurality of bits.
 10. The apparatus according to claim 8, wherein,during initial transmission, the output bit sequence includesinformation bits and parity bits that correspond to weight-2 columns.11. The apparatus according to claim 8, wherein the starting position isdetermined based on a redundancy version number.
 12. The apparatusaccording to claim 11, wherein the redundancy version number is obtainedthrough signaling.
 13. The apparatus according to claim 11, wherein theredundancy version number is obtained based on a sequence of redundancyversion numbers and a value of i, wherein i is an integer greater thanor equal to 0, the value of i indicates an i^(th) transmission.
 14. Theapparatus according to claim 13, wherein the sequence of the redundancyversion numbers is read from a memory, or the sequence of the redundancyversion numbers is determined based on an initial transmission coderate.
 15. A non-transitory computer readable medium, wherein thenon-transitory computer readable medium stores instructions that areexecutable by a computer, and the instructions comprise instructions to:obtain a size N_(CB) of a coded block, wherein the coded block isobtained based on low-density parity-check (LDPC) code and stored in acircular buffer; obtain a starting position of an output bit sequence inthe coded block, wherein a value of the starting position is one of {p₀,p₁, p₂, p₃}, wherein p₀=0, p₁, p₂, and p₃ are integers based on the sizeN_(CB) of the coded block, wherein 0<p₁<p₂<p₃≤N_(CB), and p₂−p₁<p₃−p₂;output the output bit sequence, wherein the output bit sequencecomprises a plurality of bits starting from the starting position in thecoded block; perform interleaving on the output bit sequence to generatean interleaved output bit sequence; generate one or more modulationsymbols based on the interleaved output bit sequence; output the one ormore modulation symbols; and transmit a transmission signal comprisingthe one or more modulation symbols.